If there were any Ted Cruz supporters in the crowd, they did not make themselves known. Attendees cheered for O'Rourke, and groaned for and laughed at Cruz.

The room was jolted, and let out a whoop at the mention of their city during the debate.

In a question about health insurance, O'Rourke spoke about "Joey in Laredo," who is uninsured, and was told by a doctor that he will likely die at 40. O'Rourke believes in improving the Affordable Care Act, expanding Medicaid and eventually achieving universal health care.

Pedro Herrejon, 22, who watched the debate at Cultura, just moved back to Laredo after graduating from Texas A&M in College Station.

He said when he was in high school he was a Cruz supporter. But then he realized Cruz was disingenuous, Herrejon said.

"It was a lot of lies. So when Beto O'Rourke came along, it was the complete opposite of what Ted Cruz represents. He actually stands up for what he believes in," Herrejon said.